Earth-boring tools for forming wellbores in subterranean earth formations may include a plurality of cutting elements secured to a body. For example, fixed-cutter earth-boring rotary drill bits (also referred to as “drag bits”) include a plurality of cutting elements that are fixedly attached to a bit body of the drill bit, conventionally in pockets formed in blades and other exterior portions of the bit body. Rolling cone earth-boring drill bits include a plurality of cutters attached to bearing pins on legs depending from a bit body. The cutters may include cutting elements (sometimes called “teeth”) milled or otherwise formed on the cutters, which may include hardfacing on the outer surfaces of the cutting elements, or the cutters may include cutting elements (sometimes called “inserts”) attached to the cutters, conventionally in pockets formed in the cutters. Other bits might include impregnated bits that typically comprise a body having a face comprising a superabrasive impregnated material, conventionally a natural or synthetic diamond grit or thermally stable diamond elements dispersed in a matrix of surrounding body material or segments of matrix material brazed to the bit body.
The cutting elements used in such earth-boring tools often include polycrystalline diamond cutters (often referred to as “PDCs”), which are cutting elements that include a polycrystalline diamond (PCD) material. Such polycrystalline diamond cutting elements are formed by sintering and bonding together relatively small diamond grains or crystals under conditions of high temperature and high pressure in the presence of a catalyst (such as, for example, cobalt, iron, nickel, or alloys and mixtures thereof) to form a layer of polycrystalline diamond material on a cutting element substrate. These processes are often referred to as high-temperature/high-pressure (or “HTHP”) processes. The cutting element substrate may comprise a cermet material (i.e., a ceramic-metal composite material) such as, for example, cobalt-cemented tungsten carbide. In such instances, the cobalt (or other catalyst material) in the cutting element substrate may be drawn into the diamond grains or crystals during sintering and serve as a catalyst material for forming a diamond table from the diamond grains or crystals. In other methods, powdered catalyst material may be mixed with the diamond grains or crystals prior to sintering the grains or crystals together in an HTHP process.
Exposed portions of cutting elements, such as, for example, diamond tables, portions of substrates, hardfacing disposed on the outer surfaces of cutting elements, and exposed surfaces of the earth-boring tool, for example, blade surfaces and fluid courses and junk slot surfaces of a drag bit or the cutters of a rolling cone bit, may be subject to failure modes, such as, for example, erosion, fracture, spalling, and diamond table delamination due to abrasive wear, impact forces, and vibration during drilling operations from contact with the formation being drilled. Some portions of the earth-boring tool may be more susceptible to such failure modes, and localized wear and localized impact damage may cause the earth-boring tool to fail prematurely while leaving other portions of the earth-boring tool in a usable condition. For example, cutting elements and the blades to which they are attached may be more susceptible to failure at the shoulder region of a face of the bit body as compared to the central portion of the face of the bit body or gage region of the bit body. In such instances, an annular shaped groove may wear into the face of the bit body at the shoulder region, a phenomenon sometimes referred to as “ring out” or “pocket damage.” Further, cutting elements and the blades to which they are attached may be susceptible to failure at a central, core region of a drill bit located on the face thereof, resulting in “core out.” Other earth-boring tools may similarly exhibit localized wear in certain portions of the earth-boring tools.